Phthalocyanines are useful as materials for painting compositions, printing inks and catalysts and as electronic materials and, in particular, they have recently been broadly investigated as materials for electrophotographic photoreceptors, materials for optical recording and materials for photo-electric conversion.
Regarding electrophotographic photoreceptors, recently, there is demand for extending the light-sensitive wavelength range of organic photoconductive materials, which have heretofore been proposed, up to the near infrared wavelength range of semiconductor lasers (780 to 830 nm) so as to use the materials as a photoreceptor for a digital recording system such as a laser printer. From this viewpoint, squalilium compounds (as described, e.g., in JP-A-49-105536 and JP-A-58-21414), (the term "JP-A" as used herein means an "unexamined published Japanese patent application"), triphenylamine trisazo compounds (as described, e.g., JP-A-61-151659) and phthalocyanine compounds (as described, e.g., JP-A-48-34189 and JP-A-57-148745) have been proposed as photoconductive materials for semiconductor lasers.
Where organic photoconductive materials are used as light-sensitive materials for semiconductor lasers, they are needed to satisfy the conditions that the light-sensitive wavelength range is extended up to a long wavelength range and that the sensitivity and durability of the photoreceptors to be formed therefrom are good. The above-mentioned organic photoconductive materials do not sufficiently meet the conditions.
In order to overcome various drawbacks of the known photoconductive materials, the materials have been investigated with respect to the relationship between the crystal form and the electrophotographic characteristics. In particular, many reports relating to phthalocyanine compounds have heretofore been disclosed.
In general, it has been known that phthalocyanine compounds have various crystal forms, depending upon the difference in the manufacture method and treating method, and that the difference in the crystal form has a great influence on the photo-electric conversion characteristics of phthalocyanine compounds, for example, with respect to copper phthalocyanine, various crystal forms of .alpha., .pi., 7/8.rho., .gamma. and .delta. are known in addition to a stable crystal form of .beta.. It has been also known that these crystal forms are mutually transferable to each other by mechanical strain force, acid treatment, organic solvent treatment or heat treatment (as disclosed, e.g., in U.S. Pat. Nos. 2,770,029, 3,100,885, 3,708,292 and 3,357,989). JP-A-50-38543 describes the difference in crystal forms of copper phthalocyanine and electrophotographic characteristics of them.
However, the above-mentioned phthalocyanine compounds which have heretofore been proposed are not sufficient in point of the light sensitivity and the durability when used as a light-sensitive material, and development of novel phthalocyanine compounds which may be satisfactorily used as a light-sensitive material is desired.